A glimpse of the Deep Space Atomic Clock in the middle bay of the General Atomics Orbital Test Bed spacecraft. (Credit: NASA)PASADENA, Calif. (NASA PR) — In deep space, accurate timekeeping is vital to navigation, but not all spacecraft have precise timepieces aboard. For 20 years, NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, has been perfecting a clock. It’s not a wristwatch; not something available in a store. It’s the Deep Space Atomic Clock (DSAC), an instrument being built for deep space exploration.Currently, most missions rely on ground-based antennas paired with atomic clocks for navigation. Ground antennas send narrowly focused signals to spacecraft, which, in turn, return the signal. NASA uses the difference in time between sending a signal and receiving a response to calculate the spacecraft’s location, velocity and path.This method, though reliable, could be made much more efficient. For example, a ground station must wait for the spacecraft to return a signal, so a station can only track one spacecraft at a time. This requires spacecraft to wait for navigation commands from Earth rather than making those decisions onboard and in real-time.The Atomic Clock, GPS Receiver, and Ultra-Stable Oscillator which make up the ...